Among the multitude of designs of the valves used in piston compressors the valves with circular or disc plates are the most common ones.
These types of valves are utilized in the major part of piston compressors, practically in all applications at various pressure differentials for comprising a wide nomenclature of gases including those contaminated.
The valves of piston compressors must meet a number of requirements of which the most crucial ones, bearing an important influence on the efficiency of the piston compressor, are the following:
low resistance of the valve determined by the pressure differential in the valve and, correspondingly, loss of power for overcoming the resistance of the valve by the gas passing therethrough:
high operational reliability.
The need for meeting these requirements is warranted by the fact that various compressors use 1 to 20% of their input power for overcoming the resistance of the valve to say nothing of the undue stoppages and down time of the piston compressors caused by the valves and reaching 20 to 70% of their total values.
In the long run these factors reduce the efficiency of piston compressors due to considerable power losses in the valve for overcoming its resistance, increase the cost of gas production and, in some cases, lead to wastage of the end product owing to disruption of technological processes.
Known in the prior art is a valve (see British Patent No. 1.025.713) comprising a seat with gas passages, at least one plate of a uniform thickness installed movably for closing and opening said seat passages under the effect of the pressure differential acting on the valve, a plate lift limiting stop, at least one spring located between the limiting stop and the plate and intended to move the plate for closing the seat passages at the beginning of valve closing and a device for aligning the plate.
The prior art valve has a number of substantial disadvantages which decrease the operational reliability of the valve, raise its resistance and complicate the alignment of the plate.
These disadvantages are as follows:
high resistances in the middle portion of the plate section as compared with the adjacent portions of said plate section due to the uniformity of the plate cross section in thickness and a maximum bending moment acting on the middle portion of the plate cross section which leads, oarticularly at large pressure differentials acting on the plate, to a reduced contact area of the plate closing portions and, as a consequence, to higher contact stresses at the points of actual contact with the seat;
high contact stresses in the plate at the point of its initial contact with the limiting stop located on the outer contour of the plate, arising due to nonsimultaneous contact of the plate surface with the limiting stop;
high resistance of the valve caused by a sharp turning of the gas flow from the seat passages to the slot created between the seat and the closing portions of the plate on opening of the valve;
complicated device for aligning the plate with the seat passages due to the necessity for making calibrated holes for the pins in the seat or limiting stop and for the use of fitted dowels.